MongoDB Schema design Student Exams - node.js

Question

I am trying to learn MongoDB with Nodejs and using mongoose, and know basic stuff, (I am from a SQL Background). I am trying to make a student exam Database.
There are multiple exams, each exam has some students, that are going to take some MCQ questions and answer the questions which I need to save.
As I am new to NoSQL, so I am looking for models for these requirements. (personal learning project)
Here are my example objects, which I need to model
// Exam Object
{
"ExamID": "1",
"ExamDate": "2021-01-01 09:00:00",
"ExamName": "Midterm Exam"
}
// student Object
{
"StudentID": "1",
"StudentName": "SOME FULL NAME"
}
// Question Object
{
"ExamQuestions":[
{
"QuestionID": "1",
"QuestionText": "SOME Long QUestion Text",
"Correct": "A",
"QuestionOptions":[
{
"Option_Title": "A",
"Option_Value": "This is Option A"
},
{
"Option_Title": "B",
"Option_Value": "This is Option B"
},
{
"Option_Title": "C",
"Option_Value": "This is Option C"
},
{
"Option_Title": "D",
"Option_Value": "This is Option D"
}
]
}
]
}
// students answer to questions Object
{
"Students":[
{
"StudentID":"1",
"Answers":[
{
"QuestionID": "1",
"ANSWER": "A"
},
{
"QuestionID": "2",
"ANSWER": "B"
},
{
"QuestionID": "3",
"ANSWER": "D"
}
]
},
{
"StudentID":"2",
"Answers":[
{
"QuestionID": "1",
"ANSWER": "B"
},
{
"QuestionID": "2",
"ANSWER": "C"
},
{
"QuestionID": "3",
"ANSWER": "A"
}
]
}
]
}

Answer 1

So with mongoDB there are two ways that I know in where you can deal with one-to-many, you have the embedded approach and referencing approach.
Embedded approach what is that?
(So I will step back a bit from your exam example cause I do not know how I can explain with that but I will try my best to break down relationships in mongo)
So with embedded lets say we have model for user post(Like in a social media app) so a post has comments right and one post can have many comments
So we can have a document like this
{
_id:54844838asd3843aereaf,
user:John Doe,
comments:[
{
usercomment:"random text",
}
]
}
So lets say that now another user were to comment then when using the embedded approach you basically pushing new comments in that array and then update that document so to have those new comments while maintaining the old ones
Second approach: Referencing
So here what happens is, if we do take that example from above about user post and comment
So what you want to do is to have two models user post model and comments model but then your user post model must make reference to the comments model what do I mean by this
So below we make a comments model
const mongoose = require('mongoose');
const commentsModel = mongoose.model(
"commentsModel",
new mongoose.Schema({
commentedUser:{type:String, required:true},
commment:{type:String, required:true}
})
)
Now we need to have a post model then have each post ref comments model
const postModel = mongoose.model(
"userPost",
new mongoose.Schema({
user:{type:String, required:true},
post:{type:String, required:true},
comments:[
{
type:mongoose.Schema.Types.ObjectId
ref:"commentsModel"
//So here I reference the commentsModel and on each entry
//I insert only the id of that comment
}
]
})
)
So now how the procedure would work is lets say you receive a comment from user you take that comment save in commentModel
Finally take that _id given back by mongoose and push to your array of comments (So key is to store that comment id in your comments array )
If my explanation did not fully make sense to you, you can refer to docs they clear
https://docs.mongodb.com/manual/tutorial/model-referenced-one-to-many-relationships-between-documents/
You can also check this blog out with regards to that for more clarity if docs don't make sense
https://medium.com/#brandon.lau86/one-to-many-relationships-with-mongodb-and-mongoose-in-node-express-d5c9d23d93c2
Final last resort is YouTube what best than to hear someone explain
https://youtu.be/t_9fgpsO_vM